Method and system for eliminating electromagnetic interference in a medical image, in real-time

ABSTRACT

In a medical apparatus including a medical imaging system and a medical position and navigation system (MPS), the medical imaging system including an imaging transmitter, periodically emitting imaging radiation and an imaging detector, the medical position and navigation system including at least one MPS transmitter periodically transmitting MPS radiation and at least one MPS detector, the MPS radiation electromagnetically interfering with at least one mode of operation of the imaging detector, a device for eliminating interference to the imaging detector caused by positioning radiation, the device comprising a synchronizer, coupled with the medical imaging system and with the medical position and navigation system, synchronizing the imaging detector and each the at least one MPS transmitter, so that neither of the at least one MPS transmitter transmits during the at least one mode of operation of the imaging detector.

FIELD OF THE DISCLOSED TECHNIQUE

The disclosed technique relates to medical imaging in general, and tomethods and systems for reducing electromagnetic interference in animage, obtained by a medical imaging system, in particular.

BACKGROUND OF THE DISCLOSED TECHNIQUE

Electromagnetic radiation medical imaging systems are known in the art.Such systems are generally used to create a representation in the formof an image of the anatomy of a region of interest of a patient. Suchelectromagnetic radiation medical imaging systems are, for example,X-ray, CT, MRI, US or PET systems.

Medical positioning systems (MPS) are known in the art. Such systems aregenerally used to track and mark the location of an object (e.g.,catheter) in or around the body of a patient. Medical positioningsystems may employ electromagnetic radiation to determine the locationof a body in a reference coordinate system. More specifically, thesesystems employ the relationship between the strength of the signalassociated with this radiation, as detected by a detector, and thedistance of this detector from the source of the radiation. For example,such medical positioning systems may include three electromagneticradiation transmitters, in the form of transmitting coils, positionedsuch that the axes normal to the plane crated by one of the turns ofeach coil are mutually orthogonal. These systems may employ detectors inthe form of one or more receiving coils, positioned such that the axes,normal to the plane crated by one of the turns of each coil, aremutually orthogonal. Each coil corresponds to an axis in a referencecoordinate frame.

A Medical imaging system may be employed in conjunction with a medicalpositioning system to obtain the image of the anatomy of a patient andthe location of an object within or on the patient. For example, duringa catheterization procedure, knowledge of the position of the catheterwithin the body of a patient, and an image of the anatomy of the regionin which the catheterization procedure is performed, may be necessary.

Reference is now made to FIG. 1, which is a schematic illustration of asystem, generally referenced 10, for navigating an object, such as adistal tip of a catheter, in conjunction with images of the anatomy of aportion of a body of a patient as, detected by a medical imaging system,which is known in the art. System 10 includes medical imaging system 28,a medical positioning system (MPS) 34, a catheter 16, a display unit 32and a table 14. Medical imaging system 28 includes an imaging radiationtransmitter 30 and an imaging radiation detector 26. Catheter 16includes a distal end 18. Distal end 18 includes magnetic positionradiation detectors (not shown). This position radiation detector may bea single coil detector or a multiple coil detector (not shown). Thedetector is operative for detecting magnetic fields. Medical positioningsystem 34 includes positioning radiation transmitters 20, 22 and 24.Positioning radiation transmitters 20, 22 and 24 are, for example, threecoils.

Display unit 32 is coupled with imaging radiation detector 26.Positioning radiation transmitters 20, 22 and 24, and catheter 16 arecoupled with medical positioning system 34. Catheter 16 is inserted to apatient 12, subjected to a treatment, and navigated towards a region ofinterest (e.g., the cardiovascular system). Imaging radiationtransmitter 30 transmits radiation that passes through patient 12. Theradiation, detected by imaging radiation detector 26, is arepresentation of the anatomy of a region of interest of patient 12. Animage representing the anatomy of the region of interest of patient 12is formed on display unit 32. The image includes catheter 16 and distalend 18. Positioning radiation transmitters 20, 22 and 24 transmitmagnetic fields which are mutually orthogonal, corresponding to axes ofa reference coordinate frame. The detector at distal end 18 detects themagnetic fields generated by positioning radiation transmitters 20, 22and 24. The detected signal is related to the position of distal end 18,for example, by the Biot Savart law, know in the art. Thus, the positionof distal end 18 is obtained by medical positioning system 34.Positioning radiation transmitters 20, 22 and 24 are located on imagingradiation detector 26 so as to register the coordinate system associatedwith imaging radiation detector 26 and the coordinate system associatedwith MPS 34 and to maximize the signal to noise ration of the signalsdetected by the positioning radiation detector.

However, imaging radiation detector 26 acquires the imaging radiationtransmitted by imaging radiation transmitter 30, concurrently withpositioning radiation transmitter 20, 22 and 24. Thus, due to theproximity of the positioning radiation transmitters to the imagingradiation detector, the magnetic field generated thereby, may affectimaging radiation detector 26. Consequently the image formed on displayunit 32 may be corrupted.

U.S. Pat. No. 6,810,110 to Pelc et al. entitled “X-Ray Tube forOperating in A Magnetic Field” is directed to a method wherein an x-raysource, including a cathode, an anode and magnetic means. The magneticmeans produce a magnetic field having magnetic field lines passing fromthe cathode to the anode to compensate or correct an otherwise undesiredmagnetic field. The magnetic means may include an electromagnet orpermanent magnets. The electromagnet may be electromagnetic windings orcoils mechanically coupled to the x-ray source. The permanent magnetsmay be integrated inside or positioned outside of the x-ray source.

U.S. Pat. No. 6,828,728 to Levinson, entitled “Processing images forremoval of artifacts” directs to a method wherein interference in anX-Ray image is removed by processing the image after the acquisitionthereof. The method to Levinson, initially identify a region in theimage, with a standard deviation below a predetermined threshold. Thisidentified region is declared to be free of artifacts. In the next step,each pixel element, on the outer edges of the imaging sensor, startingfrom the initially identified region, is cleaned. Cleaning is achievedby testing each pixel in sequence and comparing its value with the twopreceding clean neighbours in the respective row or column. If thetested pixel is determined not to have predetermined relationship withrespect to these clean neighbours, it is replaced by a pixel valuehaving a predetermined relationship with respect to the cleanneighbours. In the last step, the remaining pixels are tested. If apixel is found not to have a predetermined relationship with itsneighbouring pixels, the pixel is replaced with the average value of theneighbouring pixels.

U.S. Pat. No. 6,118,848 to Simon et al. entitled “System and methods forthe reduction and elimination of image artifacts in the calibration ofX-ray imagers” directs to a method to reduce the representation ofcalibration markers present in an X-ray image. The representations ofthe calibration markers are reduced by replacing the pixels representingthe calibration markers by pixels related to the pixels surrounding therepresentation of the calibration markers. The relationship between thesurrounding pixels and the replaced pixels may be that of the average ofthe surrounding pixels or multiple regions averaging.

U.S. Pat. No. 6,314,310 to Ben-Haim et al., entitled “X-Ray GuidedSurgical Location System with Extended Mapping Volume”, is directed to amethod for displaying anatomical features of interest in the body of apatient acquired by one or more X-ray images, with a probe, insertedinto the body of the patient. The probe includes sensing devices such asmagnetic field responsive coils for determining six-dimensional positionand orientation coordinates. During the surgery, as the probe isadvanced into the body of the patient, signals generated by the coils onthe probe are used to track the coordinates of the tool and to updateaccordingly, the display showing the image of the tool and the patient.Preferably, a new X-ray image is acquired from time to time. Accordingto the publication to Ben-Haim et al, a surgeon is able to insert andmanipulate the probe in the body of the patient under the visualguidance of an X-ray image of the body that includescontinuously-updated representation of the tool. The X-ray images isacquired during the surgical procedure and may be updated as desired.

SUMMARY OF THE PRESENT DISCLOSED TECHNIQUE

It is an object of the disclosed technique to provide a novel method andsystem for synchronizing a medical imaging system with a medicalpositioning system.

In accordance with the disclosed technique, there is thus provided adevice for eliminating interference to an imaging detector caused bypositioning radiation. A medical apparatus includes a medical imagingsystem and a medical position and navigation system (MPS). The medicalimaging system includes an imaging transmitter, periodically emittingimaging radiation and an imaging detector. The medical position andnavigation system (MPS) includes at least one MPS transmitterperiodically transmitting MPS radiation and at least one MPS detector.The MPS radiation electromagnetically interferes with at least one modeof operation of the imaging detector. The device includes asynchronizer, coupled with the medical imaging system and with themedical position and navigation system. The synchronizer synchronizesthe imaging detector and each the at least one MPS transmitter, so thatneither of the at least one MPS transmitter transmits during the atleast one mode of operation of the imaging detector.

In accordance with another embodiment of the disclosed technique, thereis thus provided a combined imaging and positioning apparatus. Thecombine imaging a positioning apparatus includes a medical imagingsystem, a medical position and navigation system and a synchronizer. Thesynchronizer is coupled with the medical imaging system and with themedical position and navigation system. The medical imaging systemobtains a representation of the anatomy of a portion of a body. Themedical imaging system includes an imaging radiation transmitter forperiodically transmitting imaging radiation and an imaging detector. Themedical position and navigation system (MPS) includes at least one MPStransmitter for transmitting MPS radiation, the MPS radiationelectromagnetically interferes with at least one mode of operation ofthe imaging detector. The medical position and navigation system (MPS)further includes and at least one MPS detector for detecting MPSradiation. The synchronizer, synchronizes the imaging detector and eachthe at least one MPS transmitter, so that neither of the at least oneMPS transmitter transmits during the at least one mode of operation ofthe imaging detector.

In accordance with a further embodiment of the disclosed technique,there is thus provided a method for eliminating interference to animaging detector caused by positioning radiation. A medical apparatusincludes a medical imaging system and a medical position and navigationsystem (MPS). The medical imaging system includes an imaging transmitterand an imaging detector. The imaging transmitter periodically emitsimaging radiation. The imaging detector periodically detects an imageframe. The medical position and navigation system includes at least oneMPS transmitter and at least one MPS detector. The MPS transmitterperiodically transmits MPS radiation. The method includes the proceduresof synchronizing the detection of image frames and the transmission ofthe MPS radiation, to be mutually exclusive in the time domain.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosed technique will be understood and appreciated more fullyfrom the following detailed description taken in conjunction with thedrawings in which:

FIG. 1 is a schematic illustration of a system, for navigating anobject, such as a distal tip of a catheter, in conjunction with imagesof the anatomy of a portion of a body of a patient as detected by amedical imaging system, which is known in the art;

FIG. 2 is a schematic illustration of a system, for navigating an objectsuch as a distal tip of a catheter in conjunction with images of theanatomy of a portion of a body of a patient as detected by a medicalimaging system, constructed and operative in accordance with anembodiment of the disclosed technique;

FIG. 3 is a schematic illustration of a system, for navigating an objectsuch as a distal tip of a catheter, in conjunction with images of theanatomy of a portion of a body of a patient, as detected by a medicalimaging system, constructed and operative in accordance with anotherembodiment of the disclosed technique;

FIG. 4 is a schematic illustration of a timing diagram, in accordancewith a further embodiment of the disclosed technique;

FIG. 5 is a schematic illustration of a timing diagram, in accordancewith another embodiment of the disclosed technique;

FIG. 6 is a schematic illustration of a method for synchronizing amedical imaging system with a medical positioning system, operative inaccordance with a further embodiment of the disclosed technique;

FIG. 7 is a schematic illustration of a method for synchronizing amedical imaging system with a medical positioning system, operative inaccordance with another embodiment of the disclosed technique;

FIG. 8 is a schematic illustration of a method for synchronizing amedical imaging system with a medical positioning system, operative inaccordance with a further embodiment of the disclosed technique;

FIG. 9 is a schematic illustration of a method for synchronizing amedical imaging system with a medical positioning system, operative inaccordance with another embodiment of the disclosed technique.

FIG. 10 is a schematic illustration of a timing diagram, in accordancewith a further embodiment of the disclosed technique;

FIG. 11 is a schematic illustration of a timing diagram, in accordancewith another embodiment of the disclosed technique;

FIG. 12, which is a schematic illustration of a method for synchronizingsystem the operation of a medical position system with a medical imagingsystem operative in accordance with a further embodiment of thedisclosed technique;

FIG. 13, which is a schematic illustration of a method for synchronizingthe operation of an MPS with a medical imaging system, operative inaccordance with another embodiment of the disclosed technique;

FIG. 14 which is a schematic illustration of a method for synchronizingthe operation of an MPS with a medical imaging system, operative inaccordance with a further embodiment of the disclosed technique; and

FIG. 15 which is a schematic illustration of a method for synchronizingthe operation of an MPS with a medical imaging system, operative inaccordance with another embodiment of the disclosed technique.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The disclosed technique overcomes the disadvantages of the prior art byproviding a method and a system to reduce the interference in real timeimages, acquired by a medical imaging system, caused by a magneticfield, generated by positioning radiation transmitters of a medicalpositioning system (MPS). According to the disclosed technique, asynchronizer synchronizes the operation of the imaging radiationdetector of the medical imaging system and the medical positioningradiation transmitters (i.e., at least one mode of operation of theimaging radiation detector and the operation of the positioningradiation transmitters are mutually exclusive in time). As a result ofthis synchronization, the positioning radiation transmitters do nottransmit positioning radiation while imaging radiation detector acquiresimaging radiation. (i.e., the operations of acquiring an image andtransmitting positioning radiation are mutually exclusive in time).According to another embodiment of the disclosed technique, the positionradiation transmitters do not transmit while the medical imaging systemsamples the acquired image frame from the imaging radiation detector(i.e., the operations of sampling an image frame and transmittingpositioning radiation are mutually exclusive in time). During the imageframe sampling period the medical imaging system samples the pixelvalues accumulated in the imaging radiation detector during the imageacquisition period.

Additionally, the imaging radiation detector is electromagneticallyshielded with metal plates to prevent the magnetic filed interferencewith the electronics thereof. Consequently, the interferences of themagnetic fields with the imaging radiation detector and the imagingradiation transmitter, is eliminated. Thus, the imaging system producesreal time images, which does not exhibit visible flaws due to magneticfield interference caused by the proximity of the positioning radiationtransmitter to the imaging radiation detector.

Reference is now made to FIG. 2, which is a schematic illustration of asystem, generally referenced 100, for navigating an object such as adistal tip of a catheter in conjunction with images of the anatomy of aportion of a body of a patient as detected by a medical imaging system,constructed and operative in accordance with an embodiment of thedisclosed technique. System 100 includes a medical imaging system 118,an MPS 124, a catheter 106, a synchronizer 126 and a table 104. Medicalimaging system 118 includes an imaging radiation transmitter 120, animaging radiation detector 116 and a display unit 122. MPS 124 includespositioning radiation transmitters 110, 112 and 114 and a positionradiation detector (not shown), operative for detecting magnetic fields,fitted on catheter 106. Positioning radiation transmitters 110, 112 and114 are, for example, three coils, positioned such that the axes, normalto the plane crated by one of the turns of the coils, are orthogonal.Catheter 106 includes a distal end 108. Distal end 108 includespositioning radiation detectors, (e.g., a single axis coil or multipleaxes coils).

Display unit 122 is coupled with medical imaging system 118. Positioningradiation transmitters 110, 112 and 114, and the position radiationdetector (not shown) fitted on tip 108 of catheter 106 are coupled withMPS 124. Synchronizer 126 is coupled to medical imaging system 118 andMPS 124.

Catheter 106 is inserted to a patient 102, subjected to a treatment, andnavigated toward a region of interest (e.g., the cardiovascular system).Imaging radiation transmitter 120 transmits radiation that passesthrough patient 102. Imaging radiation detector 116 detects an imageframe. This detection includes two modes. The first mode is acquiringthe imaging radiation and the second mode is sampling the acquired pixelvalues accumulated in the imaging radiation detector during the imageacquisition period. This acquired radiation, detected by imagingradiation detector 116, is a representation of the anatomy of a regionof interest of patient 102 in an image coordinate system. An imagerepresenting the anatomy of the region of interest of patient 102 isformed on display unit 122. This image includes catheter 106 and distalend 108. Positioning radiation transmitters 110, 112 and 114 transmitmagnetic fields which are mutually orthogonal, corresponding to an MPScoordinate system. The position detector at the distal end 18 detectsthe magnetic fields generated by positioning radiation transmitters 110,112 and 114. Synchronizer 126 enables positioning radiation transmitters110, 112 and 114 to transmit when imaging radiation detector 116 doesnot acquire imaging radiation. Synchronizer 126 disables transmitters110, 112 and 114 (i.e., at least from transmitting) when imagingradiation detector 116 acquires imaging radiation. According to anotherembodiment of the disclosed technique, synchronizer 126 enablespositioning radiation transmitters 110, 112 and 114 to transmit whenmedical imaging system 118 does not sample the acquired image from imageradiation detector 116. Synchronizer 126 disables transmitters 110, 112and 114 (i.e., at least from transmitting) when medical imaging system118 samples the acquired image from image radiation detector 116.

Reference is now made to FIG. 3, which is a schematic illustration of asystem, generally referenced 150, for navigating an object such as adistal tip of a catheter, in conjunction with images of the anatomy of aportion of a body of a patient, as detected by a medical imaging system,constructed and operative in accordance with a further embodiment of thedisclosed technique. System 150 includes a MPS 152, a medical imagingsystem 154, a display unit 178 and a synchronizer 180. MPS 152 includesa position detector 164, positioning radiation transmitters 156, 158,160 and positioning processor 162. Each of position radiationtransmitters 156, 158 and 160 may be a group of transmitters. Thesetransmitters may transmit at mutually exclusive frequencies or mutuallyexclusive time periods. Position detector 164 includes positioningradiation detectors 166, 168 and 170. Alternatively, position detector164 may include a single position radiation detector. Medical imagingsystem 154 includes imaging radiation transmitter 172, imaging radiationdetector 176 and imaging processor 174.

Synchronizer 180 and display unit 178 are coupled with imaging system154 and with MPS 152. Positioning processor 162 is coupled with positiondetector 164, with positioning radiation transmitters 156, 158, and 160,with display unit 178 and with synchronizer 180. Imaging processor 174is coupled with imaging radiation detector 176, with imaging radiationtransmitter 178, with display unit 178 and with synchronizer 180. Anobject such as a catheter (not shown) is inserted to a patient (notshown) subjected to a treatment, and navigated toward a region ofinterest (e.g., the cardiovascular system).

Imaging radiation transmitter 172 emits radiation that passes throughthe patient. Imaging radiation detector 176 detects an image frame. Thisdetection includes two modes of operation. The first mode is acquiringthe imaging radiation and the second mode is sampling the acquired pixelvalues accumulated in the imaging radiation detector during the imageacquisition period. This radiation, acquired by imaging radiationdetector 176, is a representation of the anatomy of a region of interestof the patient. Image detector 176 samples the acquired pixel values ofthe acquired imaging radiation. An image representing the anatomy of theregion of interest of the patient is formed on display unit 178. Theimage includes the catheter. Positioning radiation transmitters 156, 158and 160 transmit magnetic fields which are mutually orthogonal,corresponding to an MPS coordinate system. Positioning detector 164,detect the magnetic fields generated by positioning radiationtransmitters 156, 158 and 160. The detected signals are related to theposition of the distal end of the catheter in relation to positioningradiation transmitters 156, 158, 160. When the positioning radiationtransmitters 156, 158, 160 are mounted on the imaging radiation detector174, the coordinates system, associated with the MPS, is registered withthe coordinates system associated with imaging system. Synchronizer 178enables positioning radiation transmitters 156, 158, and 160 to transmitwhen imaging radiation detector 174 does not acquire imaging radiation.Synchronizer 178 disables transmitters 156, 158, and 160 when imagingradiation detector 174 acquires imaging radiation. According to anotherembodiment of the disclosed technique, synchronizer 180 enables thepositioning radiation transmitters 156, 158, and 160 to transmit whenmedical imaging system 154 does not sample the acquired image.Synchronizer 180 disables transmitters 156, 158, and 160 when medicalimaging system samples the acquired image.

Consequently, the interferences, caused by the magnetic fields, withimaging radiation detector 176, are eliminated. Thus, medical imagingsystem 154 produces an image, which does not exhibit visible flaws dueto magnetic field interference caused by the proximity of positioningradiation transmitters 156, 158 and 160 to imaging radiation detector176.

Reference is now made to FIG. 4 which is a schematic illustration of atiming diagram generally referenced 200, in accordance with a furtherembodiment of the disclosed technique. Timing diagram 200 includessignals 202, 204, 206 and 208. Signal 208 is the timing signalassociated with the transmission of imaging radiation by imagingradiation transmitter 172 (FIG. 3). Signals 202, 204 and 206 are thetiming signals associated with the operation of positioning radiationtransmitters 156, 158 and 160 (FIG. 3) respectively. Transmitters 156,158 and 160 (FIG. 3) are operated sequentially so as to enable thedetection of the position (and orientation) of an object, with respectto each axis of a reference coordinate frame, independently.Alternatively, positioning radiation transmitters 156, 158 and 160 maybe operated concurrently but at different frequencies.

Time period 210 is the imaging radiation transmission period. During theimaging radiation transmission period the imaging radiation transmittertransmits imaging radiation. Time period 212 is the imaging radiationnon-transmission period. During the imaging radiation non-transmissionperiod the imaging radiation transmitter does not transmit imagingradiation. Time period 214 is the positioning radiation transmissionperiod. During the positioning radiation transmission period thepositioning radiation transmitters transmit positioning radiation. Timeperiod 216 is the relative phase range. The relative phase range is therange in which the phase of either the positioning radiationtransmission period or the position radiation transmission period maychange without the two transmission periods overlapping. The relativephase is defined as the difference between the imaging radiationnon-transmission period and the positioning radiation transmissionperiod.

During time period 210, imaging radiation detector 176 (FIG. 3) acquiresimaging radiation. However, during time period 210, synchronizer 180(FIG. 3) at least disables positioning radiation transmitters 156, 158and 160 (FIG. 3) from transmitting. Consequently, the image obtained byimaging radiation detector 176 (FIG. 3) does not exhibit visible flawsdue to magnetic field interference.

According to another embodiment of the disclosed technique, MPS mayemploy more than three magnetic field transmitters. However, not all themagnetic field transmitters can be activated during the imagingradiation detector non-acquisition period. Thus, the synchronizerprevents the positioning radiation transmitters from transmitting duringthe period in which the imaging radiation detector acquires radiation,and continues after the imaging radiation detector stops acquiringradiation.

Reference is now made to FIG. 5, which is a schematic illustration oftiming diagram generally referenced 220 in accordance with a furtherembodiment of the disclosed technique. In Timing diagram 220, sixpositioning radiation transmitters are employed by the MPS. Timingdiagram 220 includes signals 222, 224, 226, 228, 230, 232 and 234.Signal 222, 224, 226, 228, 230 and 232 are the timing signals associatedwith the operation of the positioning radiation transmitters. Signal 234is associated with the operation of the imaging radiation transmitter172 (FIG. 3). During time period 236 imaging radiation transmitter doesnot transmit imaging radiation. Thus, the positioning radiationtransmitters can transmit. However, time period 236 is sufficient tooperate only positioning radiation transmitters number 1, 2, 3 and 4.During time period 238, imaging radiation transmitter transmitsradiation and the synchronizer disables the positioning radiationtransmitters from transmitting. However, after the imaging radiationtransmitter stops transmitting radiation, the synchronizer enablespositioning radiation transmitters to transmit, starting frompositioning radiation transmitter number 5.

Reference is now made to FIG. 6, which is a schematic illustration of amethod for synchronizing a medical imaging system with a MPS, operativein accordance with a further embodiment of the disclosed technique. Inprocedure 250, the periodic imaging radiation acquisition is enabled.With reference to FIG. 3, synchronizer 180 enables periodic imageacquisition and imaging radiation detector 176 acquires imagingradiation.

In procedure 252, imaging radiation is periodically transmitted whileimaging radiation acquisition is enabled. With reference to FIG. 3,image radiation transmitter 172 periodically transmits imagingradiation. After procedures 250 and 252, the method proceeds toprocedure 254.

In procedure 254, imaging radiation acquisition is disabled beforeenabling the positioning radiation transmission. With reference to FIG.3, synchronizer 180 disables the imaging radiation transmission beforeenabling the positioning radiation transmission.

In procedure 256, periodic positioning radiation transmission isenabled. With reference to FIG. 3, synchronizer 180 enables the periodicpositioning radiation transmission. After procedure 256, the methodproceeds to procedure 260.

In procedure 258, an image frame is downloaded form the imagingradiation detector while the positioning radiation transmission isenabled. The image frame forms an image on the display unit. Withreference to FIG. 3, imaging processor 174 downloads an image frame fromimaging radiation detector 176.

In procedure 260, positioning radiation transmission is disabled beforeenabling imaging radiation acquisition. With reference to FIG. 3,synchronizer 180 disables the positioning radiation transmission beforeenabling the imaging radiation transmission. After procedure 260, themethod proceeds to procedures 250 and 252.

According to another embodiment of the disclosed technique, two distinct(and may be different), preferably non-overlapping, periods, of theimaging acquisition and the positioning radiation, may overlap due to adrift in the relative phase between the two transmission periods. Forexample, with reference to FIG. 4, imaging radiation transmission period210 may drift toward positioning radiation transmission period 212. Therelative phase drift may be larger than the relative phase range 216.Thus an overlap between period 210 and period 212 will occur. Thesynchronizer delays the transmission of either the imaging radiation orthe positioning radiation.

Reference is now made to FIG. 7, which is a schematic illustration of amethod for synchronizing the operation of a MPS with a medical imagingsystem, operative in accordance with another embodiment of the disclosedtechnique. In procedure 270, imaging radiation is periodicallytransmitted and imaging radiation is periodically acquired. Withreference to FIG. 3, imaging radiation transmitter 172 periodicallytransmits imaging radiation and imaging radiation detector 176periodically acquires imaging radiation.

In procedure 272, positioning radiation is periodically transmittedwhile imaging radiation is acquired and while imaging radiation isperiodically transmitted. The positioning radiation transmission periodand the imaging radiation acquisition period are distinct and may bedifferent. With reference to FIG. 3, positioning radiation transmitters156, 158, and 160 periodically transmit positioning radiation. Afterprocedures 270 and 272, the method proceeds to procedure 274.

In procedure 272, a potential overlap between the imaging radiationacquisition period and the positioning radiation transmission period isdetected. This potential overlap is detected according to a change inthe relative phase between the two periods. The relative phase isdefined as the difference between the imaging radiation non-acquisitionperiod and the positioning radiation transmission period. With referenceto FIG. 4, the relative phase range 216 is the relative phase range inwhich the phase of either the imaging radiation acquisition period orthe positioning radiation transmission period may change without the twotransmission periods overlapping. When the combined relative phase driftof the imaging radiation acquisition period and the positioningradiation transmission period is larger than the relative phase range,then a potential overlap is detected and the method proceeds toprocedure 276. When the relative phase drift of the imaging radiationacquisition period and the positioning radiation transmission period isat most equal to the relative phase range, then no potential overlap isdetected and the method proceeds to procedures 270 and 272. Withreference to FIG. 3, synchronizer 180 detects a potential overlapbetween the imaging radiation acquisition period and the positioningradiation transmission period.

In procedure 276, the relative phase between the imaging radiationacquisition and the positioning radiation transmission is adjusted sothat no overlap occurs. With reference to FIG. 3, synchronizer 180adjusts the relative phase between the imaging radiation acquisition andthe positioning radiation transmission. After procedure 278, the methodproceeds to procedure 270 and 272.

According to a further embodiment of the disclosed technique, thesynchronizer enables the transmission of the positioning radiation whenthe end of an imaging radiation acquisition period is detected.Reference is now made to FIG. 8, which is a schematic illustration of amethod for synchronizing the operation of a MPS with a medical imagingsystem, operative in accordance with a further embodiment of thedisclosed technique. In procedure 290, the imaging radiation isperiodically acquired. With reference to FIG. 3, imaging radiationdetector 176 periodically acquires imaging radiation.

In procedure 290, imaging radiation is periodically transmitted whileimaging radiation is periodically acquired. With reference to FIG. 3,imaging radiation transmitter 172 periodically transmits imagingradiation. After procedures 290 and 292, the method proceeds toprocedure 294.

In procedure 294, the end of an imaging radiation acquisition period isdetected. With reference to FIG. 3, synchronizer 180 detects the end ofthe imaging radiation acquisition period.

In procedure 296, periodic positioning radiation transmission isenabled. With reference to FIG. 3, synchronizer 180 enables the periodicpositioning radiation transmission. After procedure 296, the methodproceeds to procedure 298.

In procedure 298, an image frame is downloaded form the imagingradiation detector while the position radiation transmission is enabled.The image frame forms an image on the display unit. With reference toFIG. 3, imaging processor 174 downloads an image frame from imagingradiation detector 176.

In procedure 300, positioning radiation transmission is disabled beforethe next imaging radiation acquisition period. With reference to FIG. 3,synchronizer 180 disables the positioning radiation transmission beforethe next imaging radiation acquisition period. After procedure 300, themethod proceeds to procedures 290 and 292.

According to another embodiment of the disclosed technique, thesynchronizer enables image acquisition when the positioning radiationtransmission is disabled. Reference is now made to FIG. 9, which is aschematic illustration of a method for synchronizing the operation of aMPS with a medical imaging system, operative in accordance with anotherembodiment of the disclosed technique. In procedure 310, positioningradiation is transmitted periodically. With reference to FIG. 3,positioning radiation transmitters 156, 158 and 160 periodicallytransmit positioning radiation. After procedure 310, the method proceedsto procedure 314.

In procedure 312, an image frame is downloaded form the imagingradiation detector while positioning radiation is transmitted. The imageframe forms an image on the display unit. With reference to FIG. 3,imaging processor 174 downloads an image frame from imaging radiationdetector 174.

In procedure 314, the end of a positioning radiation transmission periodis detected. With reference to FIG. 3, synchronizer 180 detects the endof a positioning radiation transmission period.

In procedure 316, periodic imaging radiation acquisition is enabled.With reference to FIG. 3, synchronizer 180 enables the periodic imagingradiation acquisition. After procedure 316, the method proceeds toprocedure 320.

In procedure 318, the imaging radiation is periodically transmittedwhile imaging radiation acquisition is enabled. With reference to FIG.3, imaging radiation transmitter 172 periodically transmits imagingradiation.

In procedure 320, imaging radiation acquisition is disabled before thestart of the next positioning radiation transmission period. Withreference to FIG. 3, synchronizer 180 disables the imaging radiationacquisition before the next positioning radiation transmission period.After procedure 320, the method proceeds to procedures 310 and 312.

Reference is now made to FIG. 10 which is a schematic illustration of atiming diagram generally referenced 350, in accordance with a furtherembodiment of the disclosed technique. Timing diagram 350 includessignals 352, 354, 356, 358 and 368. Signal 358 is the timing signalassociated with the image frame sampling. Signals 352, 354 and 356 arethe timing signals associated with the operation of positioningradiation transmitters 156, 158 and 160 (FIG. 3) respectively. Signal368 is the timing signal associated with the transmission of imagingradiation by imaging radiation transmitter 172 (FIG. 3) Transmitters156, 158 and 160 (FIG. 3) are operated sequentially so as to enable thedetection of the position (and orientation) of an object, with respectto each axis of an MPS coordinate system, independently. Alternatively,positioning radiation transmitters 156, 158 and 160 may be operatedconcurrently but at different frequencies. Time period 360 is the imageframe sampling period. During time period 360 the medical imaging systemsamples the pixel values accumulated in the imaging radiation detectorduring the image acquisition period. During time period 360 the medicalimaging system does not transmit imaging radiation. Time period 362 isthe imaging radiation transmission period. During the imaging radiationtransmission period the medical imaging system does not sample theaccumulated pixel values. Time period 364 is the positioning radiationtransmission period. During period 364 the positioning radiationtransmitters transmit positioning radiation. Time period 366 is therelative phase range. The relative phase range is the range in which thephase of either the image frame sampling period or the positionradiation transmission period may change without the two transmissionperiods overlapping. The relative phase is defined as the differencebetween the image frame non-sampling period and the positioningradiation transmission period.

During time period 360, medical imaging system 154 (FIG. 3) samples animage frame. However, during time period 360, synchronizer 180 (FIG. 3)at least disables positioning radiation transmitters 156, 158 and 160(FIG. 3) from transmitting. Consequently, the image sampled by medicalimaging system 154 (FIG. 3) does not exhibit visible flaws due tomagnetic field interference.

According to another embodiment of the disclosed technique, MPS mayemploy more than three magnetic field transmitters. However, not all themagnetic field transmitters can be activated during the image framenon-sampling period. Thus, the synchronizer prevents the positioningradiation transmitters from transmitting during the period in which themedical imaging system samples an image frame, and continues after themedical imaging system stops sampling an image frame.

Reference is now made to FIG. 11, which is a schematic illustration oftiming diagram generally referenced 380 in accordance with anotherembodiment of the disclosed technique. In Timing diagram 380, sixpositioning radiation transmitters are employed by the MPS. Timingdiagram 380 includes signals 382, 384, 386, 388, 390, 392, 394 and 400.Signal 382, 384, 386, 388, 390 and 392 are the timing signals associatedwith the operation of the positioning radiation transmitters. Signal 394is associated with the image frame sampling. Signal 400 is the timingsignal associated with the transmission of imaging radiation by imagingradiation transmitter 172 (FIG. 3).

During time period 396, medical imaging system transmits medical imagingradiation and does not sample an image frame. Thus, the positioningradiation transmitters can transmit. However, time period 396 issufficient to operate only positioning radiation transmitters number 1,2, 3 and 4. During time period 398 synchronizer disables the positioningradiation transmitters from transmitting. Furthermore, during timeperiod 398, the medical imaging system samples an image frame and doesnot transmit imaging radiation. However, after the sampling of the imageframe stops, the synchronizer enables positioning radiation transmittersto transmit, starting from positioning radiation transmitter number 5.

As mentioned above, according to a further embodiment of the disclosedtechnique, the transmission radiation transmission and the acquiredimage sampling are synchronized. Reference is now made to FIG. 12, whichis a schematic illustration of a method for synchronizing system theoperation of a medical position system with a medical imaging systemoperative in accordance with a further embodiment of the disclosedtechnique. In procedure 420, imaging radiation is periodicallytransmitted and imaging radiation is periodically acquired. Withreference to FIG. 3, imaging radiation transmitter 172 periodicallytransmits imaging radiation and imaging radiation detector 176periodically acquires imaging radiation. After procedure 420, the methodproceeds to procedure 424. In procedure 422, position radiation isperiodically transmitted. With reference to FIG. 3, position radiationtransmitters 156, 158 and 160 periodically transmit position radiation.

In procedure 424, the position radiation transmission is disabled beforesampling an image frame from the imaging radiation detector. Theposition radiation detector may interfere with the image frame sampling,thereby corrupting the image. With reference to FIG. 3, synchronizer 180disables the image frame sampling before enabling the positioningradiation transmission.

In procedure 426, an image frame is sampled after each image acquisitionperiod form the imaging radiation detector. The image frame forms animage on the display unit. With reference to FIG. 3, imaging detector176 samples an image frame after each image acquisition period.

In procedure 428, image frame sampling is disabled before enablingposition radiation transmission. With reference to FIG. 3, synchronizer180 disables the image frame sampling. After procedure 430 the methodreturns to procedure 422.

According to another embodiment of the disclosed technique,synchronization between the position radiation transmission and theimage frame sampling is achieved by detecting the relative phase betweenthe position radiation transmission period and the image frame samplingperiod, and adjusting this relative phase when necessary. Reference isnow made to FIG. 13, which is a schematic illustration of a method forsynchronizing the operation of an MPS with a medical imaging system,operative in accordance with another embodiment of the disclosedtechnique. In procedure 450, imaging radiation is periodicallytransmitted and imaging radiation is periodically acquired. Withreference to FIG. 3, imaging radiation transmitter 172 periodicallytransmits imaging radiation and imaging radiation detector 176periodically acquires imaging radiation. After procedure 450, the methodproceeds to procedure 454. In procedure 452, positioning radiation isperiodically transmitted while imaging radiation is acquired and whileimaging radiation is periodically transmitted. With reference to FIG. 3,positioning radiation transmitters 156, 158, and 160 periodicallytransmit positioning radiation. After procedure 454, the method proceedsto procedure 458.

In procedure 454, an image frame is sampled from the imaging radiationdetector after each position radiation acquisition period. Withreference to FIG. 3, imaging detector 176 samples an image frame aftereach image acquisition period.

In procedure 456, a potential overlap between the imaging radiationtransmission period and the image frame sampling period is detected.This potential overlap is detected according to a change in the relativephase between the two periods. The relative phase is defined as thedifference between the imaging radiation non-sampling period and thepositioning radiation transmission period. With reference to FIG. 4, therelative phase range 216 is the relative phase range in which the phaseof either the image frame sampling period or the positioning radiationtransmission period may change without the two transmission periodsoverlapping. When the combined relative phase drift of the image framesampling period and the positioning radiation transmission period islarger than the relative phase range, then a potential overlap isdetected and the method proceeds to procedure 458. When the relativephase drift of the image frame sampling period and the positioningradiation transmission period is at most equal to the relative phaserange, then, no potential overlap is detected and the method proceeds toprocedures 450 and 452. With reference to FIG. 3, synchronizer 180detects a potential overlap an image frame sampling period and thepositioning radiation transmission period.

In procedure 458, the relative phase between the image frame samplingperiod and the positioning radiation transmission period is adjusted sothat no overlap occurs. With reference to FIG. 3, synchronizer 180adjusts the relative phase between the image frame sampling period andthe positioning radiation transmission period. After procedure 460, themethod proceeds to procedure 450 and 452.

According to a further embodiment of the disclosed technique,synchronization is achieved by disabling the position radiationtransmission when the end of an image acquisition period is detected.The end of the image acquisition period marks the start of the imageframe sampling period. Reference is now made to FIG. 14 which is aschematic illustration of a method for synchronizing the operation of anMPS with a medical imaging system, operative in accordance with afurther embodiment of the disclosed technique. In procedure 480, imagingradiation is periodically transmitted and imaging radiation isperiodically acquired. With reference to FIG. 3, imaging radiationtransmitter 172 periodically transmits imaging radiation and imagingradiation detector 176 periodically acquires imaging radiation. Afterprocedure 480, the method proceeds to procedure 484.

In procedure 482, positioning radiation is periodically transmittedwhile imaging radiation is acquired and while imaging radiation isperiodically transmitted. With reference to FIG. 3, positioningradiation transmitters 156, 158, and 160 periodically transmitpositioning radiation. After procedure 482, the method proceeds toprocedure 484.

In procedure 484, the end of the image acquisition period is detected.With reference to FIG. 3, synchronizer 180 detects the end of theimaging acquisition period. After procedure 484, the method proceeds toprocedures 486 and 488.

In procedure 486, the image frame is sampled from the imaging radiationdetector. With reference to FIG. 3, imaging detector 176 samples theimage frame after each image acquisition period.

In procedure 488, the position radiation transmission is disabled whilethe image frame is sampled. With reference to FIG. 3, synchronizer 180disables positioning radiation transmitters 156, 158 and 160.

In procedure 490, the image frame sampling is disabled before the startof the next position radiation transmission period. With reference toFIG. 3, synchronizer 180 disables image frame sampling before the startof the next position radiation transmission period. After procedure 490the method returns to procedure 484

In accordance with another embodiment of the disclosed technique,synchronization is achieved by disabling the image frame sampling whenthe end of a position radiation transmission period is detected. FIG. 15which is a schematic illustration of a method for synchronizing theoperation of an MPS with a medical imaging system, operative inaccordance with another embodiment of the disclosed technique. Inprocedure 510, imaging radiation is periodically transmitted and imagingradiation is periodically acquired. With reference to FIG. 3, imagingradiation transmitter 172 periodically transmit imaging radiationimaging radiation detector 176 periodically acquires imaging radiation.After procedure 510, the method proceeds to procedure 514.

In procedure 512, positioning radiation is periodically transmittedwhile imaging radiation is acquired and while imaging radiation isperiodically transmitted. With reference to FIG. 3, positioningradiation transmitters 156, 158, and 160 periodically transmitpositioning radiation. After procedure 5124, the method proceeds toprocedure 514.

In procedure 516, the end of the position radiation transmission periodis detected. With reference to FIG. 3, synchronizer 180 detects the endof the imaging acquisition period.

In procedure 516, the image frame is sampled from the imaging radiationdetector. With reference to FIG. 3, imaging detector 176 samples theimage frame after each image acquisition period.

In procedure 518, image frame sampling is disabled before the start ofthe next position radiation transmission period. With reference to FIG.3, synchronizer 180 disables image frame samples before the start of thenext position radiation transmission period. After procedure 518 themethod returns to procedure 512.

It will be appreciated by persons skilled in the art that the disclosedtechnique is not limited to what has been particularly shown anddescribed hereinabove. Rather the scope of the disclosed technique isdefined only by the claims, which follow.

The invention claimed is:
 1. In a medical apparatus including a medicalimaging system and a medical position and navigation system (MPS), themedical imaging system including an imaging transmitter periodicallyemitting imaging radiation and a separate imaging detector having atleast an imaging radiation acquisition mode of operation and a samplingmode of operation, the MPS including at least one MPS transmitterperiodically transmitting MPS radiation and at least one MPS detector,with one of the at least one MPS transmitter and the at least one MPSdetector being positionable within a body, said MPS radiationelectromagnetically interfering with at least one of said modes ofoperation of said imaging detector, a device for eliminatinginterference to the imaging detector caused by positioning said MPSradiation, the device comprising: a synchronizer configured to becoupled with said medical imaging system and with said MPS, wherein saidsynchronizer is configured to synchronize said imaging detector and saidat least one MPS transmitter, so that said at least one MPS transmitterdoes not transmit during said at least one of said modes of operation ofsaid imaging detector, wherein said at least one of said modes ofoperation of said imaging detector is includes said imaging radiationacquisition mode.
 2. The device according to claim 1, wherein said atleast one of said modes of operation of said imaging detector is alsoincludes said sampling mode, and wherein said synchronizer is furtherconfigured to synchronize said imaging detector and said at least oneMPS transmitter, so that said at least one MPS transmitter does nottransmit during said sampling mode.
 3. A combined imaging andpositioning apparatus comprising: a medical imaging system, forobtaining a representation of the anatomy of a portion of a body, saidmedical imaging system including an imaging radiation transmitter forperiodically transmitting imaging radiation and a separate imagingdetector having at least an imaging radiation acquisition mode ofoperation and a sampling mode of operation; a medical position andnavigation system (MPS), said MPS including at least one MPS transmitterfor transmitting MPS radiation, said MPS radiation electromagneticallyinterfering with at least one of said modes of operation of said imagingdetector, and at least one MPS detector for detecting MPS radiation,with one of said at least one MPS transmitter and said at least one MPSdetector being positionable within the body; and a synchronizer coupledwith said medical imaging system and with said MPS, wherein saidsynchronizer is configured to synchronize said imaging detector and saidat least one MPS transmitter, so that said at least one MPS transmitterdoes not transmit during said at least one of said modes of operation ofsaid imaging detector, wherein said at least one of said modes ofoperation of said imaging detector is includes said imaging radiationacquisition mode.
 4. The system according to claim 3, wherein said atleast one of said modes of operation of said imaging detector is alsoincludes said sampling mode, and wherein said synchronizer is furtherconfigured to synchronize said imaging detector and said at least oneMPS transmitter, so that said at least one MPS transmitter does nottransmit during said sampling mode.
 5. The apparatus according to claim3, further including a display unit coupled with said medical imagingsystem and said medical positioning system, said display unit fordisplaying said representation of said anatomy in conjunction with theposition of an object.
 6. The system according to claim 5, wherein saidmedical imaging system further includes an imaging processor coupledwith said imaging radiation transmitter, coupled with said imagingradiation detector, coupled with said display unit, and coupled withsaid synchronizer, said imaging processor for controlling the operationof said imaging radiation transmitter and said imaging radiationdetector.
 7. The system according to claim 5, wherein said MPS furtherincludes a positioning processor coupled with said at least one MPStransmitter, coupled with said at least one MPS detector, coupled withsaid display unit, and coupled with said synchronizer, said positioningprocessor for controlling the operation of said at least one MPStransmitter and said at least one MPS detector.
 8. The system accordingto claim 3, wherein said positioning MPS radiation is includeselectromagnetic radiation.
 9. The system according to claim 8, whereinsaid at least one MPS detector comprises at least one coil.
 10. Thesystem according to claim 8, wherein said at least one MPS transmittercomprises at least one coil.
 11. The system according to claim 3,wherein said at least one MPS transmitter is in close proximity withsaid imaging detector and moves therewith, thereby maintainingregistration between an MPS coordinate system associated with said MPSand with an imaging coordinate system associated with said imagingsystem.
 12. The device according to claim 3, wherein said imagingdetector comprises electromagnetic shielding.
 13. The system accordingto claim 5, wherein said object is includes a catheter.
 14. The systemaccording to claim 13, wherein at least one of said at least one MPSdetector is fitted on a distal end of said catheter.
 15. In a medicalapparatus including a medical imaging system and a medical position andnavigation system (MPS), the medical imaging system including an imagingtransmitter periodically emitting imaging radiation and a separateimaging detector having at least an imaging radiation acquisition modeof operation and a sampling mode of operation, the MPS including atleast one MPS transmitter periodically transmitting MPS radiation and atleast one MPS detector, with one of the at least one MPS transmitter andthe at least one MPS detector being positionable within a body, said MPSradiation electromagnetically interfering with at least one of saidmodes of operation of said imaging detector, a device for eliminatinginterference to the imaging detector caused by MPS radiation, the devicecomprising: a synchronizer configured to synchronize said imagingdetector and said at least one MPS transmitter, so that said at leastone MPS transmitter does not transmit during said at least one of saidmodes of operation of said imaging detector, wherein said at least oneof said modes of operation of said imaging detector includes saidsampling mode.
 16. The device of claim 15, further comprising an x-raydetector configured to activate the synchronizer to synchronize saidimaging detector and said at least one MPS transmitter.
 17. A combinedimaging and positioning apparatus comprising: a medical imaging system,for obtaining a representation of the anatomy of a portion of a body,said medical imaging system including an imaging radiation transmitterfor periodically transmitting imaging radiation and a separate imagingdetector having at least an imaging radiation acquisition mode ofoperation and a sampling mode of operation; a medical position andnavigation system (MPS), said MPS including at least one MPS transmitterfor transmitting MPS radiation, said MPS radiation electromagneticallyinterfering with at least one of said modes of operation of said imagingdetector, and at least one MPS detector for detecting MPS radiation,with one of said at least one MPS transmitter and said at least one MPSdetector being positionable within the body; and a synchronizerconfigured to synchronize said imaging detector and said at least oneMPS transmitter, so that said at least one MPS transmitter does nottransmit during said at least one of said modes of operation of saidimaging detector, wherein said at least one of said modes of operationof said imaging detector includes said sampling mode.
 18. The apparatusaccording to claim 17, further including a display unit coupled withsaid medical imaging system and said medical positioning system, saiddisplay unit for displaying said representation of said anatomy inconjunction with the position of an object.
 19. The system according toclaim 18, wherein said medical imaging system further includes animaging processor coupled with said imaging radiation transmitter,coupled with said imaging radiation detector, coupled with said displayunit, and coupled with said synchronizer, said imaging processor forcontrolling the operation of said imaging radiation transmitter and saidimaging radiation detector.
 20. The system according to claim 18,wherein said MPS further includes a positioning processor coupled withsaid at least one MPS transmitter, coupled with said at least one MPSdetector, coupled with said display unit, and coupled with saidsynchronizer, said positioning processor for controlling the operationof said at least one MPS transmitter and said at least one MPS detector.21. The system according to claim 17, wherein said MPS radiationincludes electromagnetic radiation.
 22. The system according to claim21, wherein said at least one MPS detector comprises at least one coil.23. The system according to claim 21, wherein said at least one MPStransmitter comprises at least one coil.
 24. The system according toclaim 17, wherein said at least one MPS transmitter is in closeproximity with said imaging detector and moves therewith, therebymaintaining registration between an MPS coordinate system associatedwith said MPS and with an imaging coordinate system associated with saidimaging system.
 25. The device according to claim 17, wherein saidimaging detector comprises electromagnetic shielding.
 26. The systemaccording to claim 18, wherein said object includes a catheter.
 27. Thesystem according to claim 26, wherein at least one of said at least oneMPS detector is fitted on a distal end of said catheter.